Alcohol may significantly disturb thermal regulatory centers in the human. Under circumstances of varying environmental temperature exposure, this will interfere with normal homeostatic mechanisms. These mechanisms are highly dependent on skin blood flow for which previously technology was not available for reliable measurement. Xenon/133 is an inert highly diffusible gas which can be used for the determination of skin blood flow. This material will be used to measure skin perfusion in forty volunteer male subjects between the ages of eighteen and forty at three different controlled environmental temperatures. The influence of alcohol on skin blood flow will be studied in twenty of the volunteers, while the other twenty will be given a placebo. Measurements will reflect not only the influence of environmental temperature but also that of alcohol on skin blood flow. The results of this investigation will provide clinically useful knowledge of basic normal physiology and of the disturbances associated with alcohol and/or extremes of ambient temperature.